Still Hungry After Drinking your Fruit Juice? This is Why

A new study shows that fructose, a type of sugar used to sweeten processed foods and soft drinks, increases food cravings.

Published in the journal PNAS, researchers have found that fructose produced greater activity in some areas of the brain responsible for reward processing and some areas that controlled food cravings compared to glucose, another type of sugar.

The study involved asking 24 healthy volunteers to rate their desire to eat on a scale of one to 10. They were then asked to drink a glass of cherry-flavored liquid that contained two and a half ounces of fructose one day and a glass sweetened with glucose on another day.

Then, they were presented with images of high-calorie foods while doing a brain scan. They were again asked to rate their desire to eat using the same scale and if they would rather have food now or receive a monetary bonus a month later instead.

Data showed that fructose drinkers chose to eat the high-calorie food immediately than wait for the monetary reward.

This might have something to do with unreleased indicators, stimulated by glucose but not fructose, that tells the brain that “you’ve eaten” said senior author Dr. Kathleen A. Page, an assistant professor of clinical medicine at the Keck School of Medicine of the University of South California.

“Insulin is released when we consume glucose,” she said. “Fructose doesn’t stimulate insulin secretion, and if there’s no insulin, you don’t get the information that you’re full.”

Fructose is found in small amounts in fruit, honey and corn syrup. It is, however, plentiful in soft drinks and processed food. Table sugar is a mix of both fructose and glucose.

Is fructose a reason to stop eating fruits?

“Don’t stop eating fruit,” said Dr. Page. “It has a relatively low amount of sugar compared with processed foods and soft drinks — maybe 5 grams in an orange, compared with 25 grams in a 12-ounce can of soda. And it is packed with fiber, which helps slow down the absorption of food, which makes you feel full.”